Long Ago, Long Time Ago
noun, の adjective
The kanji and the word are exactly the same. That means they share meanings as well. This is a good way to start stories, by the way: 昔々に… (Long, long ago).
むかし
The reading is the same as the one you learned with the kanji. むかし sounds like a kun'yomi reading, doesn't it? It's so long.
ここは昔、山だったんだよ。
This place used to be a mountain a long time ago.
コウイチはただの昔の友人です。
Koichi is just an old friend.
昔、一回だけ、テレビ画面にキスしたことがあるよ。
I once kissed the TV screen a long time ago.